The S25B is an electric-condenser microphone that has been designed for acoustic bass. All of the parameters that are problematic for the double bass have been addressed. To be able to get the most gain before feedback it uses a very tight pattern to give a high rejection to surrounding noise, at the same time reproducing accurately the subtleties of the bass.

As placement is especially important with an instrument that has a fine finish and varying dimensions, this microphone's attachment mechanism is designed to secure the mic to the bass in different positions taking seconds to attach. This mechanism is fitted with natural soft suede so as not to mark or mar instrument. The String Bass mic is suspended in a 4-point isolation ring eliminating sympathetic vibrations and handling noise.

The SP25B is the same microphone element as the S25B. The preamp in the SP25B is upgraded to the "super pre-amp" which has 2 XLR outputs, one with ground lifted isolation transformer split, and a quarter inch line driver output.